This is an application for a new Program Project to expand knowledge of basic cardiorespiratory and cellular physiology through studies on the influece of selected environmental factors. It is focused on the effects of changing pressure, either induced differentially (e.g, water immersion) in whole animal or applied uniformly (hydrostatic compression) in tissues. This approach simulates both the hydrostatic compression of certain organ systems encountered by man at maximal depth and cardiorespiratory interactions of man whenever he is submerged at any depth. Both immersion and exposure to high pressure produce changes in cardiovascular, respiratory, renal, endocrine, and thermoregulatory functions. Although some of these changes are qualitatively similar in both cases, the underlying mechanisms are fundametally different. The specific aims of this program are to conduct comprehensive studies on the effects of immersion on varous physiological systems in whole animal, and to evaluate separately the effects of hi0gh pressure in various tissues. Project 1 will deal with the control of cardiovascular, renal and 02 delivery systems during immersion in man (Subproject A) and in a conscious dog model (Subprotect B); Projects 2-5 will study in vitro the effect of high hydrostatic and/or 02 pressure on 02 and CO2 transport in human blood (Project 2), electromechanical phenomena in mammalian cardiac muscle (Project 3), epithelial transport (Project 4), and gas phase diffusion processes (Project 5). Collectively, these studies will answer many critical questions regarding the cardiorespiratory performance of man submerged in deep water, and will help define those factors that limit exposure to hyperbaric environments. This research will be conducted in the Department of Physiology using a specially designed immersion tank and small hyperbaric chambers for tissue experiments.